/*
 * Copyright 1999-2017 Alibaba Group Holding Ltd.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package studio.raptor.sqlparser.visitor.functions;

import static studio.raptor.sqlparser.visitor.SQLEvalVisitor.EVAL_VALUE;
import static studio.raptor.sqlparser.visitor.SQLEvalVisitor.EVAL_VALUE_NULL;

import studio.raptor.sqlparser.ast.SQLExpr;
import studio.raptor.sqlparser.ast.expr.SQLMethodInvokeExpr;
import studio.raptor.sqlparser.visitor.SQLEvalVisitor;

public class Ascii implements Function {

  public final static Ascii instance = new Ascii();

  public Object eval(SQLEvalVisitor visitor, SQLMethodInvokeExpr x) {
    if (x.getParameters().size() == 0) {
      return SQLEvalVisitor.EVAL_ERROR;
    }
    SQLExpr param = x.getParameters().get(0);
    param.accept(visitor);

    Object paramValue = param.getAttributes().get(EVAL_VALUE);
    if (paramValue == null) {
      return SQLEvalVisitor.EVAL_ERROR;
    }

    if (paramValue == EVAL_VALUE_NULL) {
      return EVAL_VALUE_NULL;
    }

    String strValue = paramValue.toString();
    if (strValue.length() == 0) {
      return 0;
    }

    int ascii = strValue.charAt(0);
    return ascii;
  }
}
